Technical Field
Embodiments of the present disclosure relate generally to voltage regulators, and more specifically to techniques for stabilizing a voltage regulator for operation with a wide range of output capacitances.
Related Art
A voltage regulator receives an unregulated voltage as input and provides a regulated voltage as output. For improving regulation, an output capacitor (not included in the voltage regulator) is usually connected at the output node at which the voltage regulator generates the regulated output voltage. The specific value of the output capacitor may be different based on the requirements of the application environment. For example, if better regulation is required, the output capacitor may be chosen to have a larger capacitance value, and vice-versa. Thus, a voltage regulator may need to be designed to operate for a wide range of output capacitance values.
As is well known in the relevant arts, a voltage regulator employs closed-loop feedback, and stability of the closed-loop (or simply of the voltage regulator) is typically required to be ensured. The capacitance of the output capacitor forms a pole in the transfer function of the closed-loop, and the specific value of the output capacitance generally affects the stability of the closed-loop.
Compensation circuits are generally implemented within a voltage regulator to make the closed-loop stable. Stability of the closed-loop depends on the positions of all the poles and zeros in the closed-loop. The wide range of possible output capacitance values generally complicates the design of the compensation circuits within the voltage regulator, and may require trade-offs in the design of the voltage regulator. For example, one possible technique to ensure stability is to design the voltage regulator to have a dominant internal pole (lowest-frequency pole in the loop due to circuits or components implemented within the voltage regulator), thereby minimizing the effect of the pole due to the output capacitance on the loop stability. However, such an approach may reduce the bandwidth of the voltage regulator, thereby resulting in poor transient performance, and hence may not be desirable at least for such reason.
Hence, it is generally desirable to design a voltage regulator such that loop-stability is ensured for a wide range of possible output capacitance values.